Investigating life‐history traits of Steller sea lions with multistate hidden Markov mark–recapture models: Age at weaning and body size effects

Hastings, Kelly K.; Johnson, Devin S.; Pendleton, Grey W.; Fadely, Brian S.; Gelatt, Thomas S.

doi:10.1002/ece3.6878

Cited by 9 publications

(32 citation statements)

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“…With this study, we aimed to explore variation in age‐ and sex‐specific vital rates to improve ecological understanding that can inform future management and recovery actions under the Endangered Species Act. In general, survival rates estimated in this study for the eastern portion of the wDPS range were similar to (or higher than) previous estimates (Fritz et al, 2014; Maniscalco et al, 2015; Pendleton et al, 2006; York, 1994) and those estimated for the eastern distinct population segment (DPS) (Hastings et al, 2011, 2021; Wright et al, 2017). However, survival rates for the western portion of the wDPS range (western and central Aleutian Islands) estimated here for the first time are notably lower than those in the eastern portion of the range, particularly for male pups, yearlings of both sexes, and juvenile females aged 2–5.…”

Section: Discussionsupporting

confidence: 89%

“…However, females can compensate for smaller pup size by increasing maternal investment and/or weaning later (Lee et al, 1991; Trillmich, 1990), providing support for the assertion that maternal care influences first‐year survival more than birth mass for otariids (Boyd, 1990; McMahon & Hindell, 2003). Hastings et al (2021) found that in certain rookeries in both the eastern and western DPSs, earlier weaned yearlings had a lower probability of survival and that heavier pups were more likely to wean by one year of age. Applying these concepts to our findings, it is possible that the larger pups in the western portion of the range incur a larger burden on lactating females (as was found in South American sea lions, Otaria flavescens , who foraged longer for heavier pups; Drago et al, 2021) and may habitually be weaned sooner and therefore ultimately experience lower survival rates despite their larger size.…”

Section: Discussionmentioning

confidence: 99%

“…Specifically, basin‐scale processes such as the Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), and the Aleutian Low (AL) can cause localized changes in sea surface temperature (SST), upwelling, wind, and chlorophyll concentrations, which can affect the level of storminess or the distribution, density, and abundance of prey. The availability of prey can in turn affect foraging effort, energetic demands, the timing of weaning, reproductive output, and survival (Antonelis et al, 1997; Hastings et al, 2021; Trites & Porter, 2002). On the one hand, sea lions are flexible foragers with numerous target prey species and can therefore likely adapt to both short‐ and long‐term environmental variability (Loughlin et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Environmental drivers of demography and potential factors limiting the recovery of an endangered marine top predator

et al. 2022

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Understanding what drives changes in wildlife demography is fundamental to the conservation and management of depleted or declining populations, though making inference about the intrinsic and extrinsic factors that influence survival and reproduction remains challenging. Here we use mark-resight data from 2000 to 2018 to examine the effects of environmental variability on age-specific survival and natality for the endangered western distinct population segment (wDPS) of Steller sea lions (Eumetopias jubatus) in Alaska, USA. Though this population has been studied extensively over the last four decades, the causes of divergent abundance trends that have been observed across the wDPS range remain unknown. We developed a Bayesian multievent mark-resight model that accounts for female reproductive state uncertainty. Annual survival probabilities for male pups (0.44; 0.36-0.53), female yearlings (0.63; 0.49-0.73), and male yearlings (0.62; 0.51-0.71) born in the western portion of the wDPS range, estimated here for the first time, were lower than those in the eastern portion of the wDPS range, estimated as: male pups (0.69; 0.65-0.74), female yearlings (0.76; 0.71-0.81), and male yearlings (0.71; 0.65-0.78). There was a higher proportion of young female breeders in the western portion of the range, but overall natality was lower (0.69; 0.47-0.96) than in the eastern portion of the range (0.80; 0.74-0.84). Additionally, pup mass had a positive effect on pup survival in the eastern portion of the range and a negative effect in the western portion of the range, potentially due to earlier weaning of heavier pups. Local-and basin-scale oceanographic features such as the Aleutian Low, the Arctic Oscillation Index, the North Pacific Gyre Oscillation, chlorophyll concentration, upwelling, and wind in certain seasons were correlated with vital rates. However, drawing strong inferences from these correlations is challenging given that relationships between ocean conditions and an adaptive top predator in a dynamic ecosystem are exceedingly complex. This study provides the first demographic rate estimates for the western portion of the range where abundance estimates continue to decline. These results will advance efforts to identify factors driving

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Environmental drivers of demography and potential factors limiting the recovery of an endangered marine top predator

et al. 2022

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“…Resighting surveys of marked animals occurred at all rookeries and major haulouts in Southeast Alaska during dedicated large-scale boat-based surveys and one field camp each summer from 2002 to 2019 (Hastings et al, 2011;Pendleton et al, 2006) Few Steller sea lion females (1.9%-3.7%) can have both a dependent juvenile and pup during the pupping season (aka "triad"), in which case most often the juvenile is favored over the new pup by the end of the pupping season (Hastings et al, 2021;Maniscalco & Parker, 2009). Of 211 females With-Juvenile*year, only four (1.9%) were also observed with a pup during the survey window, and for these four cases, the pup data were replaced with the juvenile sightings.…”

Section: Field Data Collectionmentioning

confidence: 99%

“…juvenile survival in the north, compared to population stability, large population size, smaller neonates, lower juvenile survival, higher survival cost of weaning for juveniles, and more extensive animal movements in the south, where the population is considered near carrying capacity (Hastings et al, 2011(Hastings et al, , 2021Jemison et al, 2018;Mathews et al, 2011;Pitcher et al, 2007). Therefore, regional differences in reproductive output may indicate female response to variation in environmental productivity and/or local abundance.…”

Section: T a X O N O M Y C L A S S I F I C A T I O Nmentioning

confidence: 99%

Age‐specific reproduction in female Steller sea lions in Southeast Alaska

Hastings,

Jemison,

Pendleton

et al. 2023

Ecology and Evolution

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Age‐, region‐, and year‐specific estimates of reproduction are needed for monitoring wildlife populations during periods of ecosystem change. Population dynamics of Steller sea lions (Eumetopias jubatus) in Southeast Alaska varied regionally (with high population growth and survival in the north vs. the south) and annually (with reduced adult female survival observed following a severe marine heatwave event), but reproductive performance is currently unknown. We used mark‐resighting data from 1006 Steller sea lion females marked as pups at ~3 weeks of age from 1994 to 1995 and from 2001 to 2005 and resighted from 2002 to 2019 (to a maximum age of 25) to examine age‐, region‐, and year‐specific reproduction. In the north versus the south, age of first reproduction was earlier (beginning at age 4 vs. age 5, respectively) but annual birth probabilities of parous females were reduced by 0.05. In an average year pre‐heatwave, the proportion of females with pup at the end of the pupping season peaked at ages 12–13 with ~0.60/0.65 (north/south) with pup, ~0.30/0.25 with juvenile, and ~0.10 (both regions) without a dependent. In both regions, reproductive senescence was gradual after age 12: ~0.40, 0.40, and 0.20 of females were in these reproductive states, respectively, by age 20. Correcting for neonatal mortality, true birth probabilities at peak ages were 0.66/0.72 (north/south). No cost of reproduction on female survival was detected, but pup production remained lower (−0.06) after the heatwave event, which if sustained could result in population decline in the south. Reduced pup production and greater retention of juveniles during periods of poor prey conditions may be an important strategy for Steller sea lions in Southeast Alaska, where fine‐tuning reproduction based on nutritional status may improve the lifetime probability of producing pups under good conditions in a variable and less productive environment.

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Diving behavior, foraging strategies, and energetics of female Steller sea lions during early lactation

Olivier

Andrews

Burkanov

et al. 2022

Journal of Experimental Marine Biology and Ecology

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Investigating life‐history traits of Steller sea lions with multistate hidden Markov mark–recapture models: Age at weaning and body size effects

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 9 publications

References 112 publications

Environmental drivers of demography and potential factors limiting the recovery of an endangered marine top predator

Environmental drivers of demography and potential factors limiting the recovery of an endangered marine top predator

Age‐specific reproduction in female Steller sea lions in Southeast Alaska

Diving behavior, foraging strategies, and energetics of female Steller sea lions during early lactation

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